Establishing transmission format parameters between communication devices

ABSTRACT

Systems and methods for establishing transmission format parameters between communication devices are provided. In some aspects, a method includes identifying, by a first base station, a first communication session with a first user equipment. A master set of transmission format parameters is shared between the first base station and the first user equipment. The method also includes assigning a first subset of the master set of transmission format parameters to the first communication session. The first subset is specifically assigned to the first communication session and specifies which of the master set of transmission format parameters is allocated for use in the first communication session. The method also includes transmitting an indicator of the first subset to the first user equipment.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of co-pending U.S. patentapplication Ser. No. 13/831,409, filed Mar. 14, 2013, titled “Systemsand Methods fir Establishing Transmission Format Parameters BetweenCommunication Devices,” which claims the benefit of U.S. ProvisionalPatent Application Ser. No. 61/709,058, titled “Codebook Indication andSubset Restriction for Long Term Evolution,” filed on Oct. 2, 2012, bothof which are hereby incorporated by reference in their entireties forall purposes,

TECHNICAL FIELD

The subject technology generally relates to communications and, inparticular, relates to systems and methods for establishing transmissionformat parameters between communication devices.

BACKGROUND

In wireless communications, channel state information (CSI) may refer tochannel properties of a communication link between communicationdevices. This information may describe how a signal propagates from atransmitter to a receiver, and can represent the combined effect of, forexample, scattering, fading, and/or power decay with distance betweenthe transmitter and the receiver. The CSI may make it possible to adapttransmissions to current channel conditions, thereby allowing reliablecommunication to be achieved with high data rates in multi-antennasystems.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide furtherunderstanding of the subject technology and are incorporated in andconstitute a part of this specification, illustrate aspects of thesubject technology and together with the description serve to explainthe principles of the subject technology.

FIG. 1 illustrates an example of a communication system, in accordancewith various aspects of the subject technology.

FIG. 2 is a block diagram that schematically illustrates a base station,in accordance with various aspects of the subject technology.

FIG. 3 is a block diagram that schematically illustrates a userequipment, in accordance with various aspects of the subject technology.

FIG. 4 illustrates an example of a method for establishing transmissionformat parameters between communication devices, in accordance withvarious aspects of the subject technology.

FIG. 5 conceptually illustrates an electronic system with whichimplementations of the subject technology may be implemented.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth to provide a full understanding of the subject technology. It willhe apparent, however, that the subject technology may be practicedwithout some of these specific details. In other instances, structuresand techniques have not been shown in detail so as not to obscure thesubject technology.

A CSI process between two communication devices may allow channelconditions to be determined between the communication devices so thatsubsequent transmissions between the devices can be configured. A CSIprocess may involve a mobile communication device receiving one or moredownlink signals (e.g., downlink Multiple-Input Multiple-Output (MIMO)signals) from a base station over a communication channel. The mobilecommunication device may also be referred to as a user equipment (UE).The base station may also he referred to as an evolved node B (eNB), andcan include a macrocell, a microcell, a picocell, a femto cell, and/orany other suitable communication device for communicating with the UE.The CSI process may also involve the UE calculating feedback based onthe received one or more downlink signals and sending the feedbackindicative of the communication channel to the base station. The basestation may configure subsequent transmissions with the UE based on thefeedback. Channel feedback of this sort is used, for example, in EvolvedUniversal Terrestrial Radio Access (E-UTRA) systems specified by the 3rdGeneration Partnership Project (3GPP). These systems may also bereferred to as Long Term Evolution (LTE) and LTE Advanced (LTE-A).

Channel feedback schemes for LTE and LTE-A systems are discussed, forexample, in 3GPP Technical Specification Group Radio Access NetworkWorking Group 1 (TSG-RAN WG1) document R1-104473, entitled “Way Forwardon 8Tx Codebook for Rel. 10 DL MIMO”; in 3GPP TSG-RAN documentR1-105067, entitled “Way Forward on CSI Feedback for Rel. 10 DL MIMO”;in 3GPP TSG-RAN WG1 document R1-103839, entitled “Design and Evaluationof Precoder Codebooks for CSI Feedback”; in 3GPP TSG-RAN WG1 documentR1-104353, entitled “Two-Component PMI Codebook for 8TX”; in 3GPP TSdocument 36.211, entitled “Evolved Universal Terrestrial Radio Access(E-UTRA); Physical Channels and Modulation”; and in 3GPP TS document36.213, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA);Physical Layer Procedures,” all of which are incorporated by referenceherein.

Aspects of the subject technology provide improved channel feedbackschemes for use in LTE, LTE-A, and/or any other suitable mobile wirelesscommunication networks. In a CSI process, the one or more downlinksignals received by a UE may be precoded with a certain precoding scheme(e.g., a set of weights that can be applied to the base stationantennas). Each precoding scheme may be represented by a precodingmatrix. In some aspects, the UE may select the preferred precodingmatrix from a codebook that is agreed upon between the UE and the basestation. The feedback calculated by the UE may be precoding feedbackthat is indicative of the precoding matrix preferred by the UE forprecoding subsequent transmissions by the base station. For example, theprecoding feedback may indicate the index of the selected precodingmatrix in the codebook. This sort of feedback may sometimes be referredto as Precoding Matrix Indication (PMI). The UE may report the PMI aswell as channel quality information (CQI) to the base station.

In LTE Release 10, for example, a codebook for the case of eight basestation antennas (8TX) is defined in 3GPP TSG-RAN WG1 documentR1-104473, cited above. The codebook may be defined per rank (e.g., pereach number of simultaneous data streams (also referred to as spatialstreams or spatial layers) that are transmitted from the base station tothe UE in the downlink MIMO signal). According to certain aspects, thebase station may restrict the codebook to a subset of which the UE mayselect the PMI from.

Up until LTE Release 10, a UE can receive data (e.g., for a CSI process)from only one base station, However, with the advent of coordinatedmultipoint (COMP) in LTE Release 11, each UE can receive data from morethan one base station (e.g., up to three base stations). A UE may engagein a different CSI process for each base station (e.g., each UE may beconfigured with a separate channel state information reference symbol(CSI-RS)). The codebook subset for PMI selection in the current standardmay be semi-statically configured by a base station via the‘codebookSubsetRestriction’ field in the radio resource control (RRC)‘AntennaInfo’ information element (IE). A restriction of the codebookmay be defined on a per transmission mode basis and may equally apply toall configured CSI processes. Without a properly configured codebooksubset restriction, a UE may report undesirable PMIs from a MU-MIMOpairing and scheduling perspective. To maximize network throughput,aspects of the subject technology provide a mechanism to control UE PMIselection on a per CSI process basis that is not yet available in thestandards.

Moreover, in LTE Release 11 and beyond, the UE may be served, on asubframe-by-subframe basis by different base stations. The optimalcodebook for each case may depend on the antenna configuration of agiven base station. In such a scenario, the feedback overhead per CSIprocess based on a union of different codebooks may become prohibitive.Furthermore, the CQI computation burden on the UE may increasedrastically.

According to various aspects of the subject technology, gains from CoMPcan be significantly improved by pairing UEs whose preferred PMIs arelargely orthogonal to one another. Such a pairing may reduce co-channelinterference amongst co-scheduled UEs and may improve not only networkthroughput, but also individual UE throughput due to increasedscheduling opportunities. However, pairing of UEs based on an extensivesearch of unrestricted PMI reporting may often times be computationallyprohibitive and may not guarantee an optimal solution when a pool ofusers to choose from is not sufficiently large. According to certainaspects, a more pragmatic approach is to restrict the PMIs that a UE canreport for each CSI process. Such a restriction may allow the groupingof users based on close-to-orthogonal PMI sets. As a result, independentoptimization based on the traffic conditions of corresponding basestations can be achieved.

In LTE Release 11, aspects of the subject technology can be incorporatedby adding a field ‘codebookSubsetRestriction’ in CSI-RS configurationmessage CSI-RS-Config. For future releases, such as LTE Release 12 andbeyond, multiple sub-codebook designs may be provided, each tailored toa specific antenna configuration to target base stations with differentantenna types and spacings. In such a case, the feedback overhead fromreporting PMI based on a union of different codebooks may increasedrastically. To solve this problem, aspects of the subject technologyprovide a signaling mechanism for each CSI-RS configuration such that aUE is assigned a particular sub-codebook to use. Since this may be aone-time message, overhead in an uplink can be reduced. This indicatorcan be over long term or short term, and can be appropriately signaledsemi-statically or dynamically.

Another advantage of using a sub-codebook and subset restrictionindication per CSI process is the reduction in UE processing,complexity, and/or power consumption. In CoMP, a UE may need to respondto a CQI/PMI request from a base station for up to four CSI processeswithin a short period of time (e.g., 4 milliseconds). Meeting such ademand may place a lot of stress on peak processing power requirementsin the UE implementation (e.g., the UE may need to search through anentire codebook multiple times to find a preferred PMI to report). Tominimize this impact, a base station can signal to a UE a sub-codebookand/or a subset restriction that can reduce the search time for PMIselection on each CSI process. Thus, the search for a preferred PMI by aUE can be tailored to the most relevant PMIs. Consequently, the responsetime from the UE can also be improved, which may result in a moreup-to-date feedback for dynamic scheduling. According to certainaspects, the codebook indication and subset restriction by a basestation can be, among other things, derived based on the past reportinghistory for the UE's CSI-RS configuration.

According to certain aspects, the signaling described above can be froma base station to a UE. The codebook subset selection and indication canalso be from the UE to the base station to reduce overhead orcomplexity. That is, the UE can determine which sub-codebook is moresuitable for given antenna configurations.

FIG. 1 illustrates an example of communication system 100, in accordancewith various aspects of the subject technology. System 100 comprises afirst base station 102, a second base station 106, a first UE 110, and asecond UE 114 in communication with one another. UE 110 or UE 114 maycomprise, for example, a cellular phone, a wireless-enabled mobilecomputer, or any other suitable type of terminal having communicationcapabilities. Base station 102 comprises one or more antennas 104 forcommunicating with base station 106 (e.g., via communication link 124),UE 114 (e.g., via communication link 122), and/or UE 110 (e.g., viacommunication link 118). Base station 106 also comprises one or moreantennas 108 for communicating with UE 110 (e.g., via communication link120). UE 110 comprises one or more antennas 112 for communicating withbase stations 102 and 106 (e.g., for receiving downlink MIMO signalsfrom base station 102 and/or 106 and for transmitting uplink signals tobase station 102 and/or 106). UE 114 also comprises one or more antennas116 for communicating with base station 102 (e.g., for receivingdownlink MIMO signals from base station 102 and for transmitting uplinksignals to base station 102).

In one or more implementations, system 100 operates in accordance withthe LTE-A specifications. In some aspects, however, system 100 mayoperate in accordance with any other suitable communication protocol.Although system 100 is shown as comprising only two base stations andtwo user equipment, it is understood that system 100 can comprise anynumber of base stations and any number of user equipment. For example,110 may communicate with more than two base stations.

According to various aspects of the subject technology, a mastercodebook (e.g., of precoding matrices) may be shared between basestation 102, base station 106, UE 114, and UE 110. Base station 102 mayassign a subset of the master codebook to a first communication sessionbetween base station 102 and UE 110, and another subset of the mastercodebook to a second communication session between base station 102 andUE 114. In some aspects, the subset assigned to the first communicationsession may be orthogonal to the subset assigned to the secondcommunication session, thereby minimizing interference between the firstand second communication sessions. Base station 106 may also assignanother subset of the master codebook to a third communication sessionbetween base station 106 and UE 110. By assigning subsets of the mastercodebook to the communication sessions with UE 110 and/or UE 114, thesearch for preferred PMIs by UE 110 and/or UE 114 can be reduced (e.g.,since UE 110 and/or UE 114 may only need to search through therespective subsets as opposed to the entire master codebook).

Although a master codebook is described herein, other transmissionformat parameters may be shared between communication devices, and asubset of any one of the transmission format parameters may be assignedto any of the communication sessions between the communication devices.In some aspects, transmission format parameters that may be sharedbetween the communication devices include a master codebook, one or morerank indications, one or more modulation schemes, one or more encodingtypes, one or more rates, and/or other suitable parameters that may beassigned to communication sessions between the communication devices. Insome aspects, the one or more modulation schemes can include QuadraturePhase Shift Keying (QPSK), Quadrature Amplitude Modulation (QAM), amodulation with coding scheme (e.g., error correction code), and/or anyother suitable modulation scheme.

FIG. 2 is a block diagram that schematically illustrates base station102, in accordance with various aspects of the subject technology. Basestation 102 comprises memory 202, channel state information (CSI) unit204 coupled to memory 202, receiver 206 coupled to CSI unit 204,transmitter 208 coupled to CSI unit 204, and one or more antennas 104coupled to receiver 206 and transmitter 208. Receiver 206 may receivesignals from other communication devices (e.g., base station 106, UE114, and/or UE 110), and transmitter 208 may transmit signals to theother communication devices. Memory 202 may store the master codebookand/or other transmission format parameters. CSI unit 204 may assignsubsets of the master codebook to different communication sessions withdifferent user equipment. According to certain aspects, theconfiguration of base station 106 may be the same or similar to theconfiguration of base station 102 shown in FIG. 2.

FIG. 3 is a block diagram that schematically illustrates UE 110, inaccordance with various aspects of the subject technology. UE 110comprises memory 302, feedback unit 304 coupled to memory 302, receiver306 coupled to feedback unit 304, transmitter 308 coupled to feedbackunit 304, and one or more antennas 112 coupled to receiver 306 andtransmitter 308. Receiver 306 may receive signals from othercommunication devices (e.g., base station 102, base station 106, and/orUE 114) and transmitter 308 may transmit signals to the othercommunication devices. Memory 302 may store the master codebook and/orother transmission format parameters. Feedback unit 304 may generatefeedback data based on subsets of the master codebook assigned todifferent communication sessions that UE 110 is engaged in with basestation 102 and/or base station 106. According to certain aspects, theconfiguration of UE 114 may be the same or similar to the configurationof UE 110 shown in FIG. 3.

According to certain aspects, the components of base station 102 and/orUE 110 as shown in FIGS. 2 and 3, respectively, may be implemented insoftware (e.g., subroutines and code). In some aspects, some or all ofthe components may be implemented in hardware (e.g., an ApplicationSpecific Integrated Circuit (ASIC), a Field Programmable Gate Array(FPGA), a Programmable Logic Device (PLD), a controller, a statemachine, gated logic, discrete hardware components, or any othersuitable devices) and/or a combination of both. Additional features andfunctions of these components according to various aspects of thesubject technology are further described in the present disclosure.

FIG. 4 illustrates an example of method 400 for establishingtransmission format parameters between communication devices, inaccordance with various aspects of the subject technology. Method 400may be implemented by base station 102 and/or UE 110 when thesecommunication devices are engaged in a first communication session withone another. However, method 400 may also be implemented bycommunication devices having other configurations. Although method 400is described herein with reference to the examples of FIGS. 1-3, method400 is not limited to these examples. Furthermore, method 400 may beimplemented in an order different from the one shown in FIG. 4.

Method 400 comprises processes S402, S404, S406, S408, S410, S412, S414,S416, S418, and S420. Processes S402, S404, S414, S416, and S418 may beimplemented by UE 110, and therefore are shown in FIG. 4 as being withinUE 110. Processes S406, S408, S410, S412, and S420 may be implemented bybase station 102, and therefore are shown in FIG. 4 as being within basestation 102. Although the processes implemented by UE 110 and basestation 102 are described as being part of method 400, the processesimplemented by UE 110 may, in certain aspects, be considered a separatemethod from the processes implemented by base station 102.

According to various aspects of the subject technology, UE 110 generatessystem information that can be used to assist base station 102 indetermining what subset of the master codebook to assign to a firstcommunication session between UE 110 and base station 102 (S402). In oneor more implementations, feedback unit 304 of UE 110 generates thesystem information. The system information may include at least one ofcapability information of UE 110 and preference information of UE 110.The capability information may include a maximum number of precodingmatrices of the master codebook that the UE 110 is capable of searchingthrough at a given time. The preference information may include one ormore preferred ones of the master set of transmission format parameters.Transmitter 308 of UE 110 transmits the system information to basestation 102 (S404).

Receiver 206 of base station 102 receives the system information from UE110 (S406). According to certain aspects, CSI unit 204 of base station102 identifies the first communication session that base station 102 andUE 110 are engaged in (S408). In some aspects, the system informationmay be transmitted by UE 110 as part of a request by UE 110 to initiatethe first communication session with base station 102. In some aspects,base station 102 may initiate the first communication session with UE110, and/or may request the system information from UE 110 prior toprocess S402. The first communication session, for example, may includea CSI process between base station 102 and UE 110. In one or moreimplementations, the CSI process may include base station 102transmitting a subset of the master codebook to UE 110, UE 110generating feedback data based on the subset, and UE 110 transmittingthe feedback data to base station 102.

According to various aspects of the subject technology, CSI unit 204 ofbase station 102 assigns a first subset of the master codebook (e.g.,stored memory 202) to the identified first communication session (S410).In one or more implementations, the first subset is specificallyassigned to the first communication session (e.g., base station 102 mayassign a new subset of the master codebook to each new communicationsession that base station 102 engages in). The first subset, forexample, may specify which precoding matrices of the master codebook areallocated for use in the first communication session. In some aspects,the first subset comprises a subset of the precoding matrices of themaster codebook. In some aspects, the first subset consists of a singleone of the precoding matrices. In such a situation, base station 102 isassigning a specific precoding matrix for UE 110 to use in the firstcommunication session.

There may be different ways that CSI unit 204 determines which subset toassign to the first communication session. In some aspects, CSI unit 204may determine the first subset for the first communication sessionindependent of another subset determined for another communicationsession. Although independently determined, the first subset maynevertheless be the same as another subset determined for anothercommunication session or may be different from another subset determinedfor another communication session.

According to certain aspects, CSI unit 204 determines the first subsetbased on information from other communication sessions, subsets, and/orother communication devices. in one or more implementations, CSI unit204 determines to assign the first subset to the first communicationsession based on the system information received from UE 110. Forexample, if the system information indicates that UE 110 is only capableof searching through a limited number of precoding matrices, then CSIunit 204 may assign only a number of precoding matrices up to thatlimited number as part of the first subset. In another example, if thesystem information indicates that UE 110 prefers certain one or moreprecoding matrices, CSI unit 204 may assign the preferred one or moreprecoding matrices as part of the first subset.

In some aspects, CSI unit 204 may observe a previous history ofcommunication with UE 110 and determine which precoding matrices of themaster codebook it should assign to the first communication sessionbased on the history. In one or more implementations, CSI unit 204 maydetermine the first subset based on a previous subset of the mastercodebook assigned to a previous communication session between basestation 102 and UE 110. For example, if use of the previous subsetresulted in optimized communications between base station 102 and UE110, CSI unit 204 may determine the first subset to be the same orsimilar to the previous subset.

In some aspects, CSI unit 204 may determine the first subset based on asecond subset of the master codebook that is assigned by CSI unit 204 toa second communication session between base station 102 and UE 114. Insuch a situation, for example, CSI unit 204 may determine the firstsubset such that interference between the first communication sessionand the second communication session can be reduced (e.g., the firstsubset may be selected to be orthogonal to the second subset). In one ormore implementations, if the master codebook is comprised of 16precoding matrices, the first subset may include precoding vectors thatare orthogonal to the precoding vectors of the second subset. In someaspects, CSI unit 204 may determine the first subset based on a distancebetween UE 110 and UE 114. For example, the greater the distance betweenUE 110 and UE 114, the less concerned that CSI unit 204 may be withinterference between the first communication session and the secondcommunication session.

In some aspects, CSI unit 204 may determine the first subset based on athird subset of the master codebook that is assigned by base station 106to a third communication session between base station 106 and UE 110. Insuch a situation, for example, CSI unit 204 of base station 102 maydetermine the first subset such that interference between the firstcommunication session and the third communication session can be reduced(e.g., the first subset may be selected to be orthogonal to the thirdsubset). In some aspects, CSI unit 204 may determine the first subsetbased on a distance between base station 102 and base station 106. Forexample, the greater the distance between base station 102 and basestation 106, the less concerned that CSI unit 204 may be withinterference between the first communication session and the thirdcommunication session. According to certain aspects, base station 106and base station 102 may communicate relevant information (e.g.,distance information, subset information, etc.) between one another viacommunication link 124, as shown in FIG. 1. In some aspects, a separatecentral system (e.g., a central server) that is connected to both basestations 102 and 106 can facilitate the transfer of the relevantinformation between base stations 102 and 106.

According to certain aspects, CSI unit 204 may generate an indicator ofthe first subset. The indicator, for example, may be a signal that canbe transmitted to UE 110 to inform UE 110 what the first subset is(e.g., so that UE 110 may generate feedback based on the first subset).According to certain aspects, subsets of the master codebook may bepredetermined between base station 102 and UE 110 For example, if themaster codebook is comprised of 16 precoding matrices, the 16 precodingmatrices may be divided into four groups of four precoding matriceseach. In one or more implementations, base station 102 and UE 110 mayhave knowledge of how the master codebook is divided prior to initiationof the first communication session. The first subset may be determinedto be any one of the four groups. Thus, the indicator of the firstsubset may convey which of the four groups is assigned to the firstcommunication session as the first subset.

Since the indicator only has to convey which of the groups of the mastercodebook is selected, and not which specific precoding matrix from theentire master codebook is selected, a memory size of the indicator ofthe first subset can be less than a minimum memory size needed. tocommunicate a selection of a specific precoding matrix from the mastercodebook. For example, if the master codebook is comprised of 16precoding matrices, a minimum of four bits may be needed to convey aselection from the master codebook. However, if the 16 precodingmatrices of the master codebook are divided into four groups of fourprecoding matrices each, then a minimum of only two bits may be neededto convey which of the four groups is assigned to the firstcommunication session as the first subset. Thus, in this example, amemory size of the indicator of the first subset may only need to be twobits as opposed to four bits, thereby reducing the bandwidth needed toconvey to UE 110 what subset of the master codebook is assigned to thefirst communication session.

According to certain aspects, transmitter 208 of base station 102transmits the indicator of the first subset to UE 110 (S412). In someaspects, the indicator of the first subset is transmitted to UE 110 aspart of one or more reference signals (e.g., Common Reference Signals(CRS) in LTE systems, and Channel State Information Reference Signals(CSI-RS) in LTE-A systems).

Receiver 306 of UE 110 receives the indicator of the first subset(S414). According to certain aspects, receiver 306 may also receiveindicators of subsets from other communication sessions. For example,receiver 306 may receive an indicator of the second subset from basestation 102 for the second communication session and/or an indicator ofthe third subset from base station 106 for the third communicationsession.

According to certain aspects, feedback unit 304 of UE 110 generatesfirst feedback data based on the first subset (e.g., as determined fromthe received indicator of the first subset) (S416). In one or moreimplementations, the first feedback data is directed to downlinkcommunication channels between the one or more antennas 104 of basestation 102 and the one or more antennas 112 of UE 110. In some aspects,feedback unit 304 calculates the first feedback data based on the one ormore reference signals received from base station 102. The firstfeedback data may include a selection of one of the precoding matricesfrom the first subset (e.g., to inform base station 102 of a preferredprecoding scheme). If the first feedback data consists of a single oneof the (precoding matrices, the first feedback data may includeconfirmation of use of the single one of the precoding matrices.

According to certain aspects, a memory size of the selection of one ofthe subset of (precoding matrices may be less than a minimum memory sizeneeded to communicate a selection of the precoding matrices from themaster codebook. This is because the selection is made from only asubset of the master codebook as opposed to a selection from the entiremaster codebook. For example, if the master codebook is comprised of 16precoding matrices, four bits may be needed to make a selection from anyone of the 16 precoding matrices. However, if the first subset iscomprised of only four of the 16 precoding matrices, only two bits maybe needed to make a selection from any one of the four precodingmatrices. According to certain aspects, since UE 110 may transmit thisselection to base station 102 over a Physical Uplink Control Channel(PUCCH), which has only a limited number of bits for allocating tofeedback data, the reduced memory size of the selection allows for areduction in the feedback bandwidth.

According to certain aspects, transmitter 308 of UE 110 may transmit thefirst feedback data to base station 102 (S418). Receiver 206 of basestation 102 receives the first feedback data from UE 110 (S420).According to one or more implementations, CSI unit 204 may decode thefirst feedback data and use this data to decide on the precoding ofsubsequent downlink transmissions to UE 110. For example, CSI unit 204may select one or more (precoding matrices from the master codebookbased on the received first feedback data. For subsequent communicationswith UE 110, base station 102 may communicate with UE 110 using theselected one or more precoding matrices.

According to various aspects, some or all of method 400 may be repeatedfor each new communication session engaged in by base station 102 and/orUE 110. In one or more implementations, base station 102 may repeatprocesses S406, S408, S410, S412, and/or S420 for each new communicationsession that base station 102 engages in. For example, base station 102may receive new system information from UE 110 (or another userequipment), identify the new communication session with UE 110, assign anew subset to the new communication session, transmit an indicator ofthe new subset to UE 110, and/or receive new feedback data that isgenerated by UE 110 based on new assigned subset.

In one or more implementations, UE 110 may repeat processes S402, S404,S414, S416, and/or S418 for each new communication session that UE 110engages in. For example, UE 110 may generate new system information,transmit the new system information to base station 102 (or another basestation), receive an indicator of a new subset assigned to the newcommunication session, generate new feedback based on new assignedsubset, and/or transmit the new feedback data to base station 102.

Furthermore, as discussed above, although a master codebook is describedherein, other transmission format parameters may be shared between basestation 102 and UE 110, and a subset of any one of the transmissionformat parameters may be assigned to any of the communication sessionsbetween these communication devices e.g., in a similar manner asdiscussed with respect to method 400).

FIG. 5 conceptually illustrates electronic system 500 with whichimplementations of the subject technology may be implemented. Electronicsystem 500, for example, can be a desktop computer, a laptop computer, atablet computer, a server, a switch, a router, a base station, areceiver, a phone, a personal digital assistant (PDA), any device forestablishing transmission format parameters, or generally any electronicdevice that transmits signals over a network. Such an electronic systemincludes various types of computer readable media and interfaces forvarious other types of computer readable media. Electronic system 500includes bus 508, processing unit(s) 512, system memory 504, read-onlymemory (ROM) 510, permanent storage device 502, input device interface514, output device interface 506, and network interface 516, or subsetsand variations thereof.

Bus 508 collectively represents all system, peripheral, and chipsetbuses that communicatively connect the numerous internal devices ofelectronic system 500. In one or more implementations, bus 508communicatively connects processing unit(s) 512 with ROM 510, systemmemory 504, and permanent storage device 502. From these various memoryunits, processing unit(s) 512 retrieves instructions to execute and datato process in order to execute the processes of the subject disclosure.The processing unit(s) can be a single processor or a multi-coreprocessor in different implementations.

ROM 510 stores static data and instructions that are needed byprocessing unit(s) 512 and other modules of the electronic system.Permanent storage device 502, on the other hand, is a read-and-writememory device. This device is a non-volatile memory unit that storesinstructions and data even when electronic system 500 is off. One ormore implementations of the subject disclosure use a mass-storage devicesuch as a magnetic or optical disk and its corresponding disk drive) aspermanent storage device 502.

Other implementations use a removable storage device (such as a floppydisk, flash drive, and its corresponding disk drive) as permanentstorage device 502. Like permanent storage device 502, system memory 504is a read-and-write memory device. However, unlike storage device 502,system memory 504 is a volatile read-and-write memory, such as randomaccess memory. System memory 504 stores any of the instructions and datathat processing unit(s) 512 needs at runtime. In one or moreimplementations, the processes of the subject disclosure are stored insystem memory 504, permanent storage device 502, and/or ROM 510. Fromthese various memory units, processing unit(s) 512 retrievesinstructions to execute and data to process in order to execute theprocesses of one or more implementations.

Bus 508 also connects to input and output device interfaces 514 and 506.Input device interface 514 enables a user to communicate information andselect commands to the electronic system. Input devices used with inputdevice interface 514 include, for example, alphanumeric keyboards andpointing devices (also called “cursor control devices”). Output deviceinterface 506 enables, for example, the display of images generated byelectronic system 500. Output devices used with output device interface506 include, for example, printers and display devices, such as a liquidcrystal display (LCD), a light emitting diode (LED) display, an organiclight emitting diode (OLED) display, a flexible display, a flat paneldisplay, a solid state display, a projector, or any other device foroutputting information. One or more implementations may include devicesthat function as both input and output devices, such as a touchscreen.In these implementations, feedback provided to the user can be any formof sensory feedback, such as visual feedback, auditory feedback, ortactile feedback; and input from the user can be received in any form,including acoustic, speech, or tactile input.

Finally, as shown in FIG. 5, bus 508 also couples electronic system 500to a network (not shown) through network interface 516. In this manner,the computer can be a part of a network of computers (such as a localarea network (“LAN”), a wide area network (“WAN”), or an Intranet, or anetwork of networks, such as the Internet. Any or all components ofelectronic system 500 can be used in conjunction with the subjectdisclosure.

Many of the above-described features and applications may be implementedas software processes that are specified as a set of instructionsrecorded on a computer readable storage medium (alternatively referredto as computer-readable media, machine-readable media, ormachine-readable storage media). When these instructions are executed byone or more processing unit(s) (e.g., one or more processors, cores ofprocessors, or other processing units), they cause the processingunit(s) to perform the actions indicated in the instructions. Examplesof computer readable media include, but are not limited to, RAM, ROM,read-only compact discs (CD-ROM), recordable compact discs (CD-R),rewritable compact discs (CD-RW), read-only digital versatile discs(e.g., DVD-ROM, dual-layer DVD-ROM), a variety of recordable/rewritableDVDs (e.g., DVD-RAM, DVD-RW, DVD+RW, etc.), flash memory (e.g., SDcards, mini-SD cards, micro-SD cards, etc,), magnetic and/or solid statehard drives, ultra density optical discs, any other optical or magneticmedia, and floppy disks. In one or more implementations, the computerreadable media does not include carrier waves and electronic signalspassing wirelessly or over wired connections, or any other ephemeralsignals. For example, the computer readable media may be entirelyrestricted to tangible, physical objects that store information in aform that is readable by a computer. In one or more implementations, thecomputer readable media is non-transitory computer readable media,computer readable storage media, or non-transitory computer readablestorage media.

In one or more implementations, a computer program product (also knownas a program, software, software application, script, or code) can bewritten in any form of programming language, including compiled orinterpreted languages, declarative or procedural languages, and it canbe deployed in any form, including as a stand alone program or as amodule, component, subroutine, object, or other unit suitable for use ina computing environment. A computer program may, but need not,correspond to a file in a file system. A program can be stored in aportion of a file that holds other programs or data (e.g., one or morescripts stored in a markup language document), in a single filededicated to the program in question, or in multiple coordinated files(e.g., files that store one or more modules, sub programs, or portionsof code). A computer program can be deployed to be executed on onecomputer or on multiple computers that are located at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

While the above discussion primarily refers to microprocessor ormulti-core processors that execute software, one or more implementationsare performed by one or more integrated circuits, such as applicationspecific integrated circuits (ASICs) or field programmable gate arrays(FPGAs). In one or more implementations, such integrated circuitsexecute instructions that are stored on the circuit itself.

Those of skill in the art would appreciate that the various illustrativeblocks, modules, elements, components, methods, and algorithms describedherein may be implemented as electronic hardware, computer software, orcombinations of both. To illustrate this interchangeability of hardwareand software, various illustrative blocks, modules, elements,components, methods, and algorithms have been described above generallyin terms of their functionality. Whether such functionality isimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.Skilled artisans may implement the described functionality in varyingways for each particular application. Various components and blocks maybe arranged differently (e.g., arranged in a different order, orpartitioned in a different way) all without departing from the scope ofthe subject technology.

it is understood that any specific order or hierarchy of blocks in theprocesses disclosed is an illustration of example approaches. Based upondesign preferences, it is understood that the specific order orhierarchy of blocks in the processes may be rearranged, or that allillustrated blocks be performed. Any of the blocks may be performedsimultaneously. In one or more implementations, multitasking andparallel processing may be advantageous. Moreover, the separation ofvarious system components in the embodiments described above should notbe understood as requiring such separation in all embodiments, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

As used in this specification and any claims of this application, theterms “base station”, “computer”, “server”, “processor”, and “memory”all refer to electronic or other technological devices. These termsexclude people or groups of people. For the purposes of thespecification, the terms “display” or “displaying” means displaying onan electronic device.

As used herein, the phrase “at least one of” preceding a series ofitems, with the term “and” or “or” to separate any of the items,modifies the list as a whole, rather than each member of the list (i.e.,each item). The phrase “at least one of” does not require selection ofat least one of each item listed; rather, the phrase allows a meaningthat includes at least one of any one of the items, and/or at least oneof any combination of the items, and/or at least one of each of theitems. By way of example, the phrases “at least one of A, B, and C” or“at least one of A, B, C” each refer to only A, only B, or only C; anycombination of A, B, and C; and/or at least one of each of A, B, and C.

The predicate words “configured to”, “operable to”, and “programmed to”do not imply any particular tangible or intangible modification of asubject, but, rather, are intended to be used interchangeably. In one ormore implementations, a processor configured to analyze and control anoperation or a component may also mean the processor being programmed toanalyze and control the operation or the processor being operable toanalyze and control the operation. Likewise, a processor configured toexecute code can be construed as a processor programmed to execute codeor operable to execute code.

A phrase such as “an aspect” does not imply that such aspect isessential to the subject technology or that such aspect applies to allconfigurations of the subject technology. A disclosure relating to anaspect may apply to all configurations, or one or more configurations.An aspect may provide one or more examples of the disclosure. A phrasesuch as an “aspect” may refer to one or more aspects and vice versa. Aphrase such as an “embodiment” does not imply that such embodiment isessential to the subject technology or that such embodiment applies toconfigurations of the subject technology. A disclosure relating to unembodiment may apply to all embodiments, or one or more embodiments. Anembodiment may provide one or more examples of the disclosure. A phrasesuch an “embodiment” may refer to one or more embodiments and viceversa. A phrase such as a “configuration” does not imply that suchconfiguration is essential to the subject technology or that suchconfiguration applies to all configurations of the subject technology. Adisclosure relating to a configuration may apply to all configurations,or one or more configurations. A configuration may provide one or moreexamples of the disclosure. A phrase such as a “configuration” may referto one or more configurations and vice versa.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment described herein as“exemplary” or as an “example” is not necessarily to be construed aspreferred or advantageous over other embodiments. Furthermore, to theextent that the term “include,” “have,” or the like is used in thedescription or the claims, such term is intended to be inclusive in amanner similar to the term “comprise” as “comprise” is interpreted whenemployed as a transitional word in a claim.

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bthe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. §112, sixth paragraph, unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.”

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but are to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more,” Unless specifically statedotherwise, the term “some” refers to one or more. Pronouns in themasculine (e.g., his) include the feminine and neuter gender (e.g., herand its) and vice versa. Headings and subheadings, if any, are used forconvenience only and do not limit the subject disclosure.

What is claimed is:
 1. A method comprising: identifying, by a first basestation, a first communication session with a first user equipment,wherein a master set of transmission format parameters is shared betweenthe first base station and the first user equipment; assigning a firstsubset of the master set of transmission format parameters to the firstcommunication session, wherein the first subset is specifically assignedto the first communication session and specifies which of the master setof transmission format parameters is allocated for use in the firstcommunication session; transmitting a first indicator of the firstsubset to the first user equipment; assigning a second subset of themaster set of transmission format parameters to a second communicationsession with the first user equipment, wherein the second subset isspecifically assigned to the second communication session independentlyof the first subset assigned to the first communication session and thesecond subset specifies which of the master set of transmission formatparameters is allocated for use in the second communication session; andtransmitting a second indicator of the second subset to the first userequipment.
 2. The method of claim 1, wherein the master set oftransmission format parameters comprises at least one of a mastercodebook, one or more rank indications, one or more modulation schemes,one or more encoding types, and one or more rates.
 3. The method ofclaim 2, wherein the master codebook comprises precoding matrices andthe first subset consists of one of the precoding matrices.
 4. Themethod of claim 1, further comprising: identifying, by the first basestation, the second communication session with the first user equipment.5. The method of claim 1, further comprising receiving first feedbackdata from the first user equipment, wherein the first communicationsession comprises a channel state information determination processbetween the first base station and the first user equipment, and whereinthe channel state information determination process comprises thetransmitting and the receiving.
 6. The method of claim 1, wherein theassigning the first subset comprises determining the first subset basedon at least one of a previous subset of the master set of transmissionformat parameters assigned to a previous communication session betweenthe first base station and the first user equipment, a third subset ofthe master set of transmission format parameters assigned by a secondbase station to a third communication session with the first userequipment, a first distance between the first base station and thesecond base station, a fourth subset of the master set of transmissionformat parameters assigned by the first base station to a fourthcommunication session with a second user equipment, a second distancebetween the first user equipment and the second user equipment, andsystem information of the first user equipment.
 7. The method of claim1, wherein the master set of transmission format parameters is sharedbetween the first base station and a second base station that assigns athird subset of the master set of transmission format parameters to athird communication session between the second base station and thefirst user equipment.
 8. The method of claim 1, further comprisingrepeating (i) the assigning with a new subset of the master set oftransmission format parameters for each new communication sessionidentified by the first base station and (ii) the transmitting with anindicator of each new assigned subset.
 9. The method of claim 8, whereineach new communication session is between the first base station and thefirst user equipment or a second user equipment.
 10. A computer programproduct comprising instructions stored in a tangible computer-readablestorage medium, the instructions comprising: instructions to identify,by a base station, a first communication session with a user equipment,wherein a master set of transmission format parameters is shared betweenthe base station and the user equipment; instructions to receive systeminformation from the user equipment; instructions to assign a firstsubset of the master set of transmission format parameters to the firstcommunication session based at least in part on the system information,wherein the first subset is specifically assigned to the firstcommunication session and specifies which of the master set oftransmission format parameters is allocated for use in the firstcommunication session; and instructions to transmit an indicator of thefirst subset to the user equipment.
 11. The computer program product ofclaim 10, wherein the system information comprises at least one ofcapability information or preference information of the user equipment.12. The computer program product of claim 11, wherein the capabilityinformation comprises a maximum number of the master set of transmissionformat parameters that the user equipment is capable of searchingthrough at a given time and the preference information comprises one ormore preferred ones of the master set of transmission format parameters.13. The computer program product of claim 10, wherein the instructionsfurther comprise: instructions to assign a second subset of the masterset of transmission format parameters to a second communication sessionbetween the base station and a second user equipment, the second subsetbeing assigned independently of the first subset.
 14. The computerprogram product of claim 13, wherein the instructions further comprise:instructions to execute to select the first subset that is orthogonal tothe second subset.
 15. A device comprising: at least one processorcircuit configured to: identify communication sessions with a userequipment, wherein a master set of transmission format parameters isshared between the device and the user equipment; assign, specificallyfor each of the communication sessions, a subset of the master set oftransmission format parameters, the subset specifying which of themaster set of transmission format parameters is allocated for use ineach of the communication sessions; and transmit to the user equipment,for each of the communication sessions, an indicator of the subsetassigned for use in each of the communications sessions.
 16. The deviceof claim 15, wherein the communication sessions are temporallynon-overlapping.
 17. The device of claim 16, wherein the at least oneprocessor circuit is configured to: assign a first subset of the masterset of transmission format parameters specifically to a firstcommunication session of the communication sessions; and assign a secondsubset of the master set of transmission format parameters specificallyto a second communication session of the communication sessions, whereinthe second subset differs from the first subset.
 18. The device of claim15, wherein the at least one processor circuit is further configured to:receive system information from the user equipment; and assign, for atleast one of the communication sessions, the subset of the master set oftransmission format parameters based at least in part on the systeminformation.
 19. The device of claim 18, wherein the system informationcomprises at least one of capability information or preferenceinformation of the user equipment.
 20. The device of claim 19, whereinthe capability information comprises a maximum number of the master setof transmission format parameters that the user equipment is capable ofsearching through at a given time and the preference informationcomprises one or more preferred ones of the master set of transmissionformat parameters.